DESCRIPTION (Adapted from applicant s abstract): Mechanisms of enzyme catalysis and regulation at the molecular level are issues fundamental to contemporary biology. Proposed are investigations of two highly regulated enzymes of carbohydrate metabolism, human brain hexokinase and porcine liver fructose-1,6-bisphosphatase. Brain hexokinase (Glucose + MgATP2- = Glucose-6-P2- + MgADP1- +H+) is the "pacemaker of glycolysis" in brain tissue and the red blood cell. Fructose 1,6-bisphosphatue (fructose 1,6-bisphosphate + H2O = fructose-6-P + phosphate) is a key, regulatory enzyme in gluconeogenesis. Pig kidney fructose 1,6-bisphosphatase has been the focus of numerous crystallographic studies. Both of these enzymes have been focal points of the research during the past 30 years; however, because of the paucity of brain hexokinase in brain tissue, most investigations until recently have centered on fructose-1,6-bisphosphatase which is present in liver tissue in relatively large quantities. The group recently cloned, expressed (in Escherichia coli), and crystallized human brain hexokinase and porcine liver fructose-1,6-bisphosphatase (identical in amino acid sequence to the kidney enzyme). Thus, essential prerequisites for modern-day structure/function investigations such as the availability of cloned genes, expression systems, large quantities of pure enzyme and crystals, are now in place. The focus here is studies in directed mutation, kinetics, NMR and crystallography as a means of defining the atomic-level mechanisms of catalysis and regulation of fructose-1,6-bisphosphatase and brain hexokinase.